DIY a Dumble Headshell: How I did it
2nd part
Someone will wonder why I didn't make a "dovetail" joint between the boards .... the wood glued with Patex vinyl glue is more resistant than steel, the four nails I use in the joints are only used for ensure a 90 degree angle between the parts and perfectly align the edges. The only attention must be paid to the excess glue which must be cleaned with a wet sponge (which must then be rinsed well otherwise it becomes hard as a codfish).
Building the box
The box is made up of 4 boards, as reported in the first part. For example, I use the regular sized Dumble chassis with two 52.7cm X 26cm boards. On them I draw a line on the shorter side one centimeter from the edge, I insert 4 nails along this line. The first and last about 2.5 cm from the edge while the other two at a distance of 6 cm from the first two therefore: Edge> 2.5 cm = nail> 6 cm = nail> 6 cm = nail> 6 cm = nail> 2.5 cm Edge.
I will use the hammer until the tips of the nails are about to come out on the opposite side of the wood. If the tip of the nail protrudes, I hit it again so that it does not bite into the wood that I am going to glue at 90 °.
I repeat this operation for the opposite side of the table and for the table that I will use as a base.
First, with the package of Patex glue that has a spout, I pour (draw) a line of glue at the bottom of the board at the points where the nails should come out. Basically I draw a line of glue one cm from the bottom edge of one side of the board.
Now I draw a line of glue in the center of the 26 cm long edge and place the edge of the large board over it where I had previously drawn a line of glue. I help match the edges to hold the large board in place with the other small board positioned towards the opposite edge of the large board. I'm going to form an inverted "U" where only one side will be glued.
Once I have checked that the edges of the boards are aligned, with small strokes I fully penetrate one of the nails 2.5 cm from the edge. If necessary, pivoting on this nail, I align the 26 cm long edge and make the other outermost nail penetrate. Then I hit the remaining nails. To check that the angle between the two boards is 90 ° I use a metal square (I repeat the measurement several times after having fixed the first nail). Now I use the 90 ° clamp to hold the angle between the two boards until the glue is dry, about 4 hours.
At this point it is much easier to attach the other two boards of the box. I assure you that the joint will be solid as a rock, it is not necessary to use dovetail cuts or screws.
Back and front closure of the headshell.
I always leave these two parts for last and I prefer to complete and cover the box so I postpone the construction to the end of the main job.
Drawing of the points where the box will be pierced.
I decide which will be the upper wall and the front of the constructed box. It is not a critical operation and I let myself be guided by the "beauty" of the wood .... sometimes I am too "precise", and to remember the choice I write "superior" on the wood with a pencil.
First of all, I draw in the upper wall of the box the perimeter of the chassis that will come into contact with it.
To do this I use a drawing of the headschell that I found on TAG.
Dumble head cab / enclosure plan:
https://ampgarage.com/forum/viewtopic.php?t=21107
M.Fowler reported the construction plan of the Headschell (headcab)
ods_head_cab_plans_180.pdf
** Attention: the measures vary slightly from those I use but as I have already written .... they are too "precise".
The method I use is: starting from the side edge of the box I draw a line 2.25 cm from it and perpendicular to the length of the box.
I then draw a line 1.5 cm from the front of the box and another line 2.0 cm. These lines will be the track for the top front dodge of the box. Then I draw two lines, which intersect the first two marked perpendicularly, at a distance of 4.3 cm from the side walls.
I draw a small line 9.5 cm from the front wall approximately in the middle of the length and on it I find and mark the point in the center of the table, exactly 26.35 cm from the side edges.
Now I draw two lines that join the points on the edge of the front wall 4.3 cm from the side walls to the point that marks half the length of the box on the small line 9.5 cm from the front wall. The inclined section that joins the front edge with the line drawn at 1.5 cm from it will constitute the cutting line of the front recess.
To have a softer connection than this offset you should use the compass but this is impossible because the support point would be outside the wood that constitutes the box. I use the edge of an overturned and leaning liqueur glass to join the lines.
To draw the precise point where to drill the table for the passage of the bolts that hold the chassis attached to the upper wall, I measure with the gauge, a precision measuring instrument, the distance of the square holes of the chassis intended to receive the cage nuts from the side wall and front of the chassis and report their measurements in the upper table. With the help of the metal square I join the marked points to form four squares. Then I draw the lines of conjunction of the vertices of the squares and obtain the center of the hole to be drilled at their intersection.
Tomorrow for the third part.
Un abbraccio
Franco
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